Stent delivery system

ABSTRACT

The present invention is a device for delivering a self-expanding stent. The device has an inner shaft and an outer shaft moveable with respect to the inner shaft. The self expanding stent is received on the inner shaft adjacent its distal end. A tapered tip is located on the inner shaft distal end and it forms a smooth transition from the delivery device to the guide wire extending therethrough. A handle allows the practitioner to deploy the stent single handedly. The stent may have its segments in a first radial configuration for deliver of the stent or the stent may have a plurality of segments in a first radial configuration and a plurality of second segments in a second radial position.

RELATED APPLICATIONS

This application is a divisional of and claims priority from U.S. patentapplication Ser. No. 09/691,650 filed Oct. 17, 2000, now U.S. Patent No.6,786,918, issued on Sep. 7, 2004.

FIELD OF THE INVENTION

The present invention relates generally to methods and devices fordelivering and deploying a medical endoprosthesis, and more particularlyto a delivery system for a self-expanding endoprosthesis.

BACKGROUND OF THE INVENTION

Medical endoprostheses, commonly referred to as stents, are known in theprior art for maintaining the patency of a diseased or weakened vesselor other passageway. Stents have been implanted in various bodypassageways such as blood vessels, the urinary tract, the biliary tract,and other body lumens. These devices are inserted into the vessel,positioned across the treatment area and then expanded or allowed toself expand to keep the vessel or passageway open. Effectively, thestent overcomes the natural tendency of the weakened area to close.Stents used in the vascular system are generally implantedtransluminally during or following percutaneous transluminalangioplasty.

Self expanding stents may be mechanically compressed springs whichexpand when released, and/or they may be constructed from shape-memorymaterials including shape memory polymers and metals such anickel-titanium (Nitinol) alloys and the like which have shape-memorycharacteristics.

Delivery devices for self expanding stents have included a protectivesheath to prevent premature expansion at body temperatures for heatinduced shape memory devices or to contain mechanically restrained orstress induced shape memory devices. The sheath also enhances thedelivery through the tortuous vessels of the vascular system. Suchsheaths increase the profile of the delivery system, necessitating useof a delivery catheter with a large diameter. The large diameter of thedelivery catheter may in turn increase the risk of complications at thepatient access site.

The increased profile also detracts from the ability of the device tonavigate through tortuous vessels or passageways. The increasedcross-sectional profile of the delivery system may make it impossible todeliver a self expanding stent to the treatment area and may decreasethe ability to deliver sufficient contrast material through the guidecatheter for enabling precise positioning.

In addition to the large profile of the delivery system, another problemassociated with self expanding stents is that the stent itself cannot beradially compressed to a low profile. Since most such stents are cutfrom a tubular member, they are limited to the radial size of the tubefrom which they were cut. As explained above, it is desirable to keepthe profile of the stent as small as possible. Furthermore, deploying aself expanding stent requires manipulating the outer sheath whilekeeping the stent carrying shaft stationary in order to properly placethe stent at the treatment site.

In the event that a distal protection device is being used during thevascular procedure, the present invention can be used for retrieving thedistal protection device. Distal protection devices are delivered via aguidewire and are positioned distal of the treatment area where they areexpanded across the vessel to capture emboli that may escape during theprocedure or placement of the stent. These devices are often selfexpanding and thus deployed and retrieved with a sheath. The procedurecan become very time consuming if the delivery system must be completelyremoved after the procedure and then the distal protection device sheathbe reinserted to withdraw the catheter. Thus, it would be an advantageto use the delivery device as the retrieval device for the distalprotection device. Therefore, what is needed is a delivery system thataddresses the problem of compressing the self expanding stent to a lowerprofile than that achieved with conventional stent delivery systems. Astent delivery system that is easy to manipulate, has a low profile andcan also accommodate a distal protection device is also needed.

SUMMARY OF THE INVENTION

The present invention is a delivery system for a self expanding stentthat has catheter with an outer shaft moveable with respect to an innershaft for releasing a stent. The stent is positioned on the inner shaftand restrained by the outer shaft until it is released at the treatmentsite. The catheter tip is mounted on the inner shaft and is tapered toprovide a smooth transition from the catheter outer shaft to theguidewire extending distally of the delivery system. A handle is locatedon the proximal end for one-handed operation when deploying the stent.

The system may include a valve relief that is selectively coupled to thecatheter. By coupling the valve relief to the hemostatic valve ortuohy-borst coupler, the catheter can be moved within the hemostaticvalve while reducing back bleed.

The catheter may deploy a stent retained in one of two configurations.In the first configuration, all the stent segments are compressedtogether and have the same radial position about the inner shaft. In thesecond configuration, certain crowns of the stent segments arepositioned within the other crowns of the stent segments such that somehave a first radial position and some have a second radial position. Thesecond position is achieved by pressing certain crowns of segmentsinward after the first stent roll down to the first position when allthe segments have the same radial position.

In alternative embodiments of the delivery system, the catheter outershaft may extend past the inner shaft. This creates an area within thedelivery system for retrieving a distal protection device.Alternatively, the inner shaft can be withdrawn sufficiently within theouter shaft to create an area to accommodate a distal protection devicefor retrieval with the delivery system catheter.

BRIEF DESCRIPTION OF DRAWINGS

For a more complete understanding of the features, aspects, andadvantages of the present invention, reference is now made to thefollowing description, appended claims, and accompanying drawingswherein:

FIG. 1 is a side elevational view of the delivery system of the presentinvention;

FIG. 2 is a cross-sectional view of the distal portion of the deliverysystem of the present invention taken along lines 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view of the proximal portion of the deliverysystem of the present invention taken along line 3-3 of FIG. 1;

FIG. 4 is a cross-section of an alternative embodiment of the distal endof the delivery system of the present invention;

FIG. 5 is a cross-sectional view taken along 5-5 of FIG. 1;

FIG. 6 is a side view of one embodiment of a self expanding stent;

FIG. 7 is a side view of an alternative embodiment of a self-expandingstent;

FIG. 8 is a cross sectional view of a reduced stent in a firstconfiguration;

FIG. 9 is a cross sectional view of a reduced stent in a secondconfiguration;

FIG. 10 is a schematic of the initial stent roll down fixture;

FIG. 11 is a schematic of placing an initially rolled down stent in atubing;

FIG. 12 is a schematic of a stent position in the final roll downfixture;

FIG. 13 is a side view of an alternative embodiment of the handle of thepresent invention;

FIG. 14 is a cross-section view of the distal end of the presentinvention when used in conjunction with a distal protection device; and

FIG. 15 is a cross-section view of another embodiment of the handle ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a system for delivering a self expanding stent.Stent delivery system, designated 10 in FIG. 1, consists of an elongatedmember 12 and a handle 14. Handle 14 includes a longitudinal slot 16along which knob 18 can reciprocate. A transverse slot 20 is located atthe distal end of longitudinal slot 16 and knob 18 can rotate and entertransverse slot 20. A strain relief 22 is located at handle 14 distalend and surrounds the proximal exterior of elongated member 12 toprovide a smooth transition between handle 14 and elongated member 12.

Turning now to FIGS. 2 and 3, elongated member 12 comprises an innershaft 24 and an outer shaft 26. The outer shaft 26 is moveable withrespect to the inner shaft 24 for releasing stent 28 at the desiredtreatment site. Outer shaft 26 is preferably a braided compositeconsisting of a nylon outer jacket, a stainless steel wire braid and apolyether block amide inner layer. Outer shaft 26 inner lumen surface 30is preferably coated, such as with silicone, to reduce friction betweenthe inner and outer shaft 26 during deployment of stent 28. Inner shaft24 is preferably made of a composite material such as a stainless steelbraid fully encapsulated in a polyimide/FEP blend. Stent 28 ispositioned on inner shaft 24 at the distal portion 32 of the elongatedmember 12 and is preferably a self expanding stent 28 made from a shapememory material such as nitinol or a mechanically compressible springmaterial. Outer shaft lumen 34 has preferably a substantially constantdiameter along the length as shown in FIG. 2, although its distalportion can be enlarged or reduced, depending upon the size of thestent, to accommodate the stent within the delivery system 10.Accordingly, distal portion 36 of outer shaft 26 has an enlarged innerlumen diameter to accommodate the stent 28 as seen in FIG. 4. Aradiopaque marker 40 is located on outer shaft distal end. Radiopaquemarker 40 enables the practitioner to view the outer shaft 26 positionduring the procedure.

As shown in FIG. 3, proximal end 42 of outer shaft 26 is secured to aslider 44 of handle 14. Slider 44 is positioned within handle housing 46and is moveable on a hypotube shaft 48 extending from distal end ofhandle 14 through handle housing 46. Proximal end 50 of hypotube shaft48 is secured to a luer fitting 52. Luer fitting 52 can be any suitableluer fitting, such as a two arm luer as shown in FIG. 3 or a one armluer as shown in FIG. 1. Knob 18 extends from the exterior of handlehousing 46 though longitudinal slot 16 into handle housing interiorwhere it is coupled to slider 44. When the practitioner manipulates knob18 along longitudinal slot 16 during deployment of the stent, outershaft 26 moves with respect to inner shaft 24. Knob 18 and slider 44 arerotatably moveable on hypotube shaft 48. When knob 18 is rotated andpositioned in transverse slot 20, it cannot translate along longitudinalslot 16 and in turn the outer shaft 26 cannot move longitudinally.Accordingly, the device is in a locked position preventing unintendeddeployment of stent 28.

Strain relief 22 includes a raised ring 54 approximate its distal end56. Annular valve relief 58 is positioned around the outer shaft 26 andhas an inner groove 60 for receiving raised ring 54 therein forreleasably securing valve relief 58 to strain relief 22. Valve relief 58allows the practitioner to selectively close the hemostatic valve ortuohy-borst coupler (together with an introducer collectivelyrepresented by the dashed line element 27) about valve relief 58,reducing back bleed while permitting free movement of the deliverysystem 10 during the procedure.

The inner shaft 24 includes an elongated tubular channel spacer 62 and atubular spacer 64 and extends from the delivery system distal portion 32through hypotube shaft 48 in handle 14 to secure at luer fitting 52.Channel spacer 62 extends coaxial along the length of inner shaft 24from a proximal marker band 66 to approximately strain relief 22. Eightchannels, 68A-68H, are spaced about its circumference as shown in FIG.5. While eight channels are shown, any suitable number of channels maybe chosen. Tubular spacer 64, also coaxial with inner shaft 24, extendsfrom the proximal end of channel spacer 62 through hypotube shaft 48 tojust distal of luer fitting 52. Hypotube shaft 48 acts as a supportcomponent for the proximal end of the inner shaft 24. Tubular spacer 64is positioned within hypotube shaft 48 to decrease the annular space 70between the hypotube shaft 48 and inner shaft 24 thus reducing theability of the inner shaft 24 to deflect in a radial direction.Furthermore, tubular spacer 64 and channel spacer 62 support inner shaft24 with respect to outer shaft 26 by eliminating slack when outer shaft26 is moved with respect to inner shaft 24. Accordingly, this acts toincrease the responsiveness of outer shaft 26 with respect to themovement of knob 18 such that there is one to one correlation betweenthe amount of movement of knob 18 and outer shaft 26.

Catheter tip 72 is coupled to distal end 74 of inner shaft 24approximate distal marker band 76. Tip 72 increases in diameter frominner shaft 24 to approximate the diameter of the outer shaft 26 at anintermediate section 78. Tip 72 then tapers in diameter to match guidewire port 80 at distal end of delivery system 10. This results in anatraumatic soft tip for smoothing the transition between guide wire 82,outer shaft 26 and guide wire port 80. Adjacent tip 72 is the stentreceiving area 84 defined by the two marker bands, proximal marker band66 and distal marker band 76. Inner shaft 24 may have a reduced crosssection (not shown) to accommodate the stent in order to maintain a lowprofile for delivery system 10. Marker bands may also form a portion ofa stop for the retained stent, such that the stent will remain inposition on the inner shaft during the procedure as the outer shaft 26is retracted during deployment. As seen in FIG. 4, proximal marker band88 is positioned under an annular stop 90 surrounding inner shaft 24 andfilling the proximal portion of stent receiving area 86 not filled bythe stent. Likewise, marker band 92 is positioned on inner shaft 24under the proximal end of catheter tip 94.

Stent 28 is a self expanding stent. A self expanding stent cut from asingle Nickel-Titanium alloy hypodermic tube in a modular configurationsuch as that shown in FIGS. 6 and 7 may be used, although any suitablestent configuration may be used. In particular, the stent of FIG. 6includes a series of tubular segments, one of which is designated 96,that consist of twelve crowns, one of which is designated 98,continuously joined in a sinusoidal pattern. This stent arrangement maybe reduced for delivery in the configuration of crowns of the stentsegments in contact with each other as shown in FIG. 8. In another stentconfiguration, the segments are staggered as shown in FIG. 7. In this,the segments alternative with different number of crowns. For example,the segment designated 102 preferably has twelve crowns and the segmentdesignated 104 has fifteen crowns. This arrangement is advantageous forreducing the stent into the configuration shown in FIG. 9 where crowns106 a-106 c have a radial position within the radial position of crowns108 a-i. While twelve and fifteen crowns are shown, any combination maybe used depending upon the stent size and the amount of scaffoldingdesired.

To load the stent 28 into delivery system 10, stent 28 is radiallyreduced in size as known in the art by rolling the stent 28 into areduced diameter and then placing the outer shaft 26 over stent 28. Moreparticularly, as shown in the schematic of FIGS. 10-11, stent 110 in itsexpanded form is placed in a conventional roll down fixture 112. Stent110 is preferably cooled, such as with liquid nitrogen, as it ismechanically rolled down. As it is rolled down, the roll down foil 112 ais pulled with handle 112 b causing stent 110 to be reduced in radialsize against wedge 112 c. Stent 110 is then pushed into a tubing 114 andthe initial roll down is complete. The stent may then be loaded onto thedelivery system 10 by placing it into inner shaft 24 and removing tubing114 as outer shaft 26 is placed over the restrained stent. As shown inFIG. 8, crowns 116 a-116 l are compressed against each other in thisfirst roll down configuration and each crown has the same radialposition about the circumference of inner shaft 24.

If it is desired to reduce stent 110 into a smaller diameter, thefollowing procedure may be used. Secondary roll down fixture 118 (FIG.12) contains a first block 120 and a second block 122. Tubing 114 andstent 110 are taken from the first roll down and placed in first block120. Stent 110 is advanced out of tubing 114, and as it emerges,selected crowns of stent segments are pushed in, decreasing the diameterof the stent 110 and enabling it to be pushed into the smaller tubing124 located in second block 122. Stent 110 is inserted into tubing 124over the inner shaft 24 and positioned between marker bands 66 and 76.Preferably every fourth crown of the stent member is pushed down, andthus as shown in FIG. 9, the inner three crowns 106 a-c have a shorterradial position about inner shaft 24 than the remaining crowns l08 a-l08i. While three crowns are shown pushed in for the stent having astaggered twelve and fifteen crown arrangement, the number of crownsdepends upon the configuration of the stent and the desired reducedradial size of the stent. Once stent 110 is loading in tubing 124 andover inner shaft 24, distal end 126 of outer shaft 26 is placed over thestent 110. As outer shaft 26 is moved distally to cover the stent 110,it pushes tubing 124 off stent 110. Stent 110 can also be cooled, suchas with liquid nitrogen, during this process to assist in the final rolldown into outer shaft 26. As outer shaft 26 is moved distally over theshaft, knob 18 is also moved to its distal position in the longitudinalslot 16 and then rotated to sit in the transverse slot 20 to preventunintended movement of outer shaft 26 and thus unintended deployment ofstent. Once tubing 124 is removed, catheter tip 72 is mounted onto innershaft 24.

In an alternative embodiment shown in FIGS. 13 and 14, longitudinal slot130 of the handle 132 extends distally past transverse slot 134. Whenknob 136 is slid in the distal direction past transverse slot 134, outershaft distal portion 138 extends past catheter tip 140.

A further embodiment is shown in FIG. 15. The inner shaft 142 extendspast the luer fitting 144 to an annular knob 146 selectively coupled tothe luer fitting 148.

When the knob 146 is released from the luer fitting 144 and movedproximally, inner shaft 142 will move proximally with respect to theouter shaft.

In use, the lumens of delivery system 10 are flushed via the luerfitting 44 with saline. An indwelling guide wire is inserted through thelumen of inner shaft 24. The catheter is inserted through the indwellingintroducer or guiding catheter (or coupling member) (an outline of sucha coupling member connected to an introducer is shown by the dashedlines 27). Valve relief 58 may be detached from the strain relief 22 andis positioned in the hemostatic valve or tuohy-borst coupler (not shown)which is then is tightened down around the valve relief 58. The stent 28is advanced through the vessel and is positioned at the treatment site.Knob 18 is slowly slid with the operator's thumb or finger in a proximaldirection along the slot 16 of handle 14 which the operator is holding.This causes outer shaft 26 to pull backwards in a proximal direction,slowly releasing the stent 28 in the vessel. The delivery system 10 isthen removed from the vessel by holding the guide wire 82 in place andpulling back on the delivery system 10 in a proximal direction.

In the event that a distal protection device is being used during thevascular procedure, the present invention can be used for retrieving thedistal protection device with the embodiments shown in FIGS. 13-15.After the stent is deployed, the delivery system of FIGS. 13 and 14 isadvanced distally up to the basket 162 of the distal protection device164. Knob 136 is slid forward in a distal direction with the operator'sthumb or finger along longitudinal slot 130 past the transverse slot134. This will result in outer shaft 138 extending past the tip 140,creating an area 160 between tip 140 and distal end of outer shaft 138into which the distal protection device basket 162 can be drawn forremoval. Both the delivery system 10 and the distal protection device164 are then removed from the vessel by pulling the delivery system 10and distal protection device 164 back in the proximal direction. Withthe embodiment of FIG. 15, knob 146 is released from the luer fitting144 and moved proximally. Inner shaft 142 will also move in a proximaldirection, creating an area 160 within the outer shaft 138 foraccommodating a distal protection device.

The foregoing embodiments and examples are illustrative and are in noway intended to limit the scope of the claims set forth herein. Forexample. These and other alternatives are within the scope of theinvention.

1. A method for mounting on a delivery system a stent comprising aplurality of tubular segments connected in series, the methodcomprising: a) reducing the plurality of tubular segments to a firstradial position, each of the tubular segments comprising a plurality ofcrowns located at the first radial position; b) moving selected crownsfrom the first radial position to a second radial position, wherein thesecond radial position is less than the first radial position; c)positioning the stent in the delivery system.
 2. A method of claim 1wherein positioning the stent in the delivery system comprises pullingthe stent into the delivery system.
 3. A method of claim 1 whereinreducing the stent to the first radial position comprises placing thestent in a roll down fixture, rolling the stent in the roll down fixturesuch that the crowns are in contact with each other, and placing therolled down stent from the roll down fixture into a tubing.
 4. A methodof claim 1 and further including cooling the stent during steps a-c. 5.A method of claim 3 wherein the delivery system comprises an inner shaftand an outer retractable shaft, said method further comprising: movingthe stent over the inner shaft and adjacent at least one marker band;and placing the stent into the outer retractable sheath.
 6. A method ofclaim 1 further comprising cutting the stent from a single hypodermictube.
 7. A method of claim 6 wherein the single hypodermic tube consistsof a nickel-titanium alloy hypodermic tube.
 8. A method of claim 7wherein the stent is a self expanding stent.
 9. A method of claim 1wherein the tubular segments comprise a sinusoidal pattern.
 10. A methodof claim 1 wherein the tubular segments alternative with a differentnumber of the crowns.
 11. A method of claim 1 wherein a first tubularsegment of the tubular segments consists of twelve crowns and a secondtubular segment of the tubular segments consists of fifteen crowns. 12.A method of claim 1 wherein three crowns of the fifteen crowns of thesecond tubular segment are moved from the first radial position to thesecond radial position during the moving selected crowns from the firstradial position to a second radial position.
 13. A method of claim 1wherein the moving selected crowns from the first radial position to asecond radial position reduces the diameter of the stent.